The invention relates to a method for authorizing the use of a motor vehicle that has at least a first antenna and a second antenna, wherein the first antenna and the second antenna are at a physical interval from one another. The motor vehicle is in particular a two- or four-wheeled motor vehicle.
In the case of such known methods, it is desirable for them to be further improved against manipulations.
An object of the invention is to provide a method for authorizing the use of a motor vehicle with improved protection against manipulations.
This object is achieved in particular by a method for authorizing the use of a motor vehicle having the features of the independent method claim. Advantageous configurations of the method according to the invention are the subject matter of the dependent method claims.
The method according to the invention proceeds from a method for authorizing the use of a motor vehicle, in particular a two- or four-wheeled motor vehicle, that has at least a first antenna and a second antenna, wherein the first antenna and the second antenna are at a physical interval from one another, by a portable identification transmitter that has an identification transmitter antenna.
This known method is developed according to the invention by the following steps.
In a first step, the first vehicle antenna emits a first signal that is received via the identification transmitter antenna.
In a second step, the identification transmitter ascertains at least one of the spatial components of the first electromagnetic field of the received first signal, preferably using an angle-resolving magnetic field sensor.
In a third step, the second vehicle antenna emits a second signal that is received via the identification transmitter antenna.
In a fourth step, the identification transmitter ascertains at least one of the spatial components of the second electromagnetic field of the received second signal, preferably using the angle-resolving magnetic field sensor.
In a fifth step, the identification transmitter transmits a measure or a value for the ascertained at least one spatial component of the first electromagnetic field of the received first signal and a measure or a value for the ascertained at least one spatial component of the second electromagnetic field of the received second signal to the vehicle.
In a sixth step, a first computer, preferably a computer in the motor vehicle, ascertains the angle at least between the ascertained spatial component of the first electromagnetic field of the received first signal and the ascertained spatial component of the second electromagnetic field of the received second signal, and in a seventh step, the motor vehicle provides an authorization signal for authorizing the use of the motor vehicle only if the ascertained angle exceeds a predetermined threshold value.
In summary, the method according to the invention allows at least two physically separate or spaced transmitters to be used to determine the position of the receiver or of the identification transmitter in angle-resolved fashion. If the signals of the spaced transmitters are forwarded by a repeater with the intention of manipulation, the delay time is extended and the angle information is lost. The angle-resolving method according to the invention can detect such manipulation of the radio link by virtue of the parallelism of the signals being detected by the identification transmitter and/or by the motor vehicle and one or both of the latter preventing the emission of an authorization signal.